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Comparison of laser-based joining approaches for plastic-metal-hybrids - stength vs. process speed

: Straeten, K. van der; Engelmann, C.; Olowinsky, A.; Gillner, A.

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Hausmann, J.M. ; Deutsche Gesellschaft für Materialkunde -DGM-:
3. Internationale Konferenz Hybrid Materials and Structures 2018. Proceedings : 18. - 19. April 2018, Bremen
Frankfurt: DGM, 2018
ISBN: 978-3-88355-417-4
"Hybrid Materials and Structure" Conference (Hybrid) <3, 2018, Bremen>
Konferenzbeitrag, Elektronische Publikation
Fraunhofer ILT ()

Especially in automotive- and aerospace industry saving weight through innovative lightweight designs is an important requirement. The multi-material lightweight construction approach opens up new paths for weight savings by using different materials adapted to local loads and mechanical requirements. While plastics are characterized by low weight, low price and nearly unlimited shaping possibilities, metals can withstand much higher loads due to their mechanical properties. In order to implement multi-material lightweight construction, suitable joining techniques are required to connect plastics and metals. The laserbased joining approach is an innovative joining technique, where no additive materials such as adhesives or fasteners are used. In a first process step laser radiation creates structures with an undercut geometry into the metal surface. In a second process step thermoplastic and metal are thermally joined together by heating up the metal and melting the polymer through heat conduction. The molten polymer flows into the cavities of the microstructured metal surface. After hardening a joint based on mechanical interlocking is created.
Currently, different approaches for microstructuring the metal surface are pursued by using different laser sources and processing strategies. These approaches mostly differ in structure topography and geometry, the resulting joint strengths and processing speeds. In this contribution two different microstructuring processes are compared: The formation of undercut grooves with a continuously emitting single mode fiber laser and the formation of spongy structures with an ultrashort pulsed laser. Advantages and disadvantages of both processes are evaluated and compared regarding structure geometry, joint strength and process speed.